Gadolinium Atoms Research Articles

Large Carbon Clusters with Entrapped Gadolinium Atoms

Gadolinium metallofullerenes have long shown promise as potential MRI contrast agents. The ability to entrap up to three gadolinium atoms permits a high concentration of metal content per fullerene cage. The protective carbon cage prevents the escape of otherwise toxic free Gd ion. In this presentation, we will discuss purification strategies to isolate gadolinium clusters entrapped within larger carbon cages (C96-C120). We have recently isolated a series of fullertubes, which consist of a nanotube belt of carbons with fullerene endcaps. It is unknown if the entrapped Gd atoms are inside fullerene or fullertube cages.

Single- and Multi-Arm Gadolinium MRI Contrast Agents for Targeted Imaging of Glioblastoma.

BackgroundPosition of gadolinium atom(s) plays a key role in contrast enhancement of gadolinium-based contrast agents. To gain a better understanding of effects of distance of gadolinium in relation to the nanoconjugate platform, we designed and synthesized single- and multi-arm (“star”) gadolinium conjugates equipped with antibody and peptides for targeting. The contrast agents were studied for their tumor imaging performance in a glioma mouse model.Materials and MethodsAntibody- and peptide-targeted nano contrast agents (NCAs) were synthesized using polymalic acid platforms of different sizes. Gadolinium-DOTA and intermediates were attached as amides and targeting agents such as antibodies and peptides as thioethers. For in vivo experiments, we used human U87MG xenografts as glioma models. Magnetic resonance imaging (MRI) was performed on a Bruker BioSpec 94/20USR 9.4 T small-animal scanner. Delivery of contrast agents across the blood–brain barrier was studied by fluorescent microscopy.ResultsAll contrast agents accumulated into tumor and showed composition-dependent imaging performance. Peptide-targeted mini-NCAs had hydrodynamic diameters in the range 5.2–9.4 nm and antibody-targeted NCAs had diameters in the range 15.8–20.5 nm. Zeta potentials were in the range of –5.4–−8.2 mV and −4.6–−8.8 mV, respectively. NCAs showed superior relaxivities compared to MultiHance at 9.4 T. The signal enhancement indicated maximum accumulation in tumor 30–60 minutes after intravenous injection of the mouse tail vein. Only targeted NCAs were retained in tumor for up to 3 hours and displayed contrast enhancement.ConclusionThe novel targeted NCAs with star-PEG features displayed improved relaxivity and greater contrast compared with commercial MultiHance contrast agent. The enhancement by mini-NCAs showed clearance of tumor contrast after 3 hours providing a suitable time window for tumor diagnosis in clinics. The technology provides a great tool with the promise of differential MRI diagnosis of brain tumors.

Ferromagnetic quasi-atomic electrons in two-dimensional electride

An electride, a generalized form of cavity-trapped interstitial anionic electrons (IAEs) in a positively charged lattice framework, shows exotic properties according to the size and geometry of the cavities. Here, we report that the IAEs in layer structured [Gd2C]2+·2e− electride behave as ferromagnetic elements in two-dimensional interlayer space and possess their own magnetic moments of ~0.52 μB per quasi-atomic IAE, which facilitate the exchange interactions between interlayer gadolinium atoms across IAEs, inducing the ferromagnetism in [Gd2C]2+·2e− electride. The substitution of paramagnetic chlorine atoms for IAEs proves the magnetic nature of quasi-atomic IAEs through a transition from ferromagnetic [Gd2C]2+·2e− to antiferromagnetic Gd2CCl caused by attenuating interatomic exchange interactions, consistent with theoretical calculations. These results confirm that quasi-atomic IAEs act as ferromagnetic elements and trigger ferromagnetic spin alignments within the antiferromagnetic [Gd2C]2+ lattice framework. These results present a broad opportunity to tailor intriguing ferromagnetism originating from quasi-atomic interstitial electrons in low-dimensional materials.

SANS analysis of aqueous dispersions of Eu- and Gd-grafted nanodiamond particles

The structure of detonation nanodiamond aqueous dispersions grafted by europium or gadolinium atoms was investigated by small-angle neutron scattering over a wide size scale from 1 to 3000 nm. Similar to the previous studies of nanodiamond suspensions, a strong association of the particle into developed aggregates was revealed. While the characteristic aggregate size depends on the modification of the dispersions and varies in a wide interval of 35–1500 nm, the fractal character of clusters of nanodiamond particles (packed in a specialized branched form with a fractal dimension of 2.4) remains unchanged independent of the cluster size. The effect of the aggregate size increase upon grafting is considered as a basis for the stability reduction mechanism at the microstructural level.

Template-controlled on-surface synthesis of a lanthanide supernaphthalocyanine and its open-chain polycyanine counterpart

Phthalocyanines possess unique optical and electronic properties and thus are widely used in (opto)electronic devices, coatings, photodynamic therapy, etc. Extension of their π-electron systems could produce molecular materials with red-shifted absorption for a broader range of applications. However, access to expanded phthalocyanine analogues with more than four isoindoline units is challenging due to the limited synthetic possibilities. Here, we report the controlled on-surface synthesis of a gadolinium-supernaphthalocyanine macrocycle and its open-chain counterpart poly(benzodiiminoisoindoline) on a silver surface from a naphthalene dicarbonitrile precursor. Their formation is controlled by the on-surface high-dilution principle and steered by different metal templates, i.e., gadolinium atoms and the bare silver surface, which also act as oligomerization catalysts. By using scanning tunneling microscopy, photoemission spectroscopy, and density functional theory calculations, the chemical structures along with the mechanical and electronic properties of these phthalocyanine analogues with extended π-conjugation are investigated in detail.

In-Situ Growth of Gadolinium Phthalocyaninato Sandwich Complexes on the Ag(111) Surface.

We report a low-temperature scanning tunneling microscopy investigation of the in-situ growth of gadolinium phthalocyaninato complexes by combined deposition of free-base phthalocyanines and gadolinium atoms on a smooth Ag(111) substrate. A careful control of the stoichiometry allows the expression of a multilevel structurecomposed of irregularly distributed Gdx-1 (Pc)x complexes, x=2-5, thus paving new avenues for surface-confined columnar growth.

Monte Carlo Modeling of Magnetic Phase Transitions in Amorphous Alloys of the Re–Gd System

A Monte Carlo study of the magnetic properties of simulated amorphous alloys of the Re–Gd system is performed using the Heisenberg model. The temperature dependences of spontaneous magnetization, magnetic susceptibility, and the Edwards–Anderson order parameter are calculated. The dependence of the temperature of the transition to the spin-glass state on the concentration of gadolinium atoms is constructed. The transition to the spin-glass state in Re–Gd amorphous alloys occurs only above the percolation threshold in this system.

THE METHOD FOR OBTAINING A DERIVATIVE CLOSO-DECABORATE ANION WITH PENDANTE DTPA-GROUP

This paper describes the method for obtaining a new derivative of the closo-decaborate anion with diethylenetriaminepentaacetic acid (DTPA) as a pendant group attached to the boron cluster through an alkoxyl spacer chain. This derivative is formed by the interaction of 1,4-dioxane derivative of the anion [B10H10]2- with DTPA potassium salt in an aqueous medium. As a result of the reaction, an exo-polyhedral cyclic substituent is opened, and then the addition of a polyfunctional group through an oxygen atom occurs. The synthesized compound is in fact an effective polydentate ligand capable of coordinating to the complexing agent both due to the donor atoms of the attached DTPA fragment and through the formation of three-center two-electron bonds. The obtained compound interacts with gadolinium(III) carbonate forming a complex of the composition [Gd2B10H9O2C4H8(dtpa)]·3H2O. The synthesized substances were studied by IR spectroscopy, polynuclear (11B, 13C and 1H) NMR spectroscopy, ESI mass spectrometry, elemental and thermographic analysis. closo-Decaborate with the pendant DTPA group is of interest in 10B neutron capture therapy of malignant tumors due to the high content of boron atoms and a convenient way of their transport to the affected cells. The obtained boron-containing derivatives of gadolinium(III) can act as drugs of combined action, because they can perform, in addition to the above described therapeutic function, the diagnostic function due to the presence of gadolinium atoms int hem.

States of Atoms and Interatomic Interactions in Perovskite-Type Oxides: XIX. Magnetic Susceptibility of the La1–yGdyAlO3 Solid Solutions

The La1–yGdyAlO3 (y = 0.01–0.15) solid solutions have been studied using the magnetic dilution method. Antiferromagnetic exchange between gadolinium atoms located in the lanthanum sites has been revealed.

Interactions between Endohedral Metallofullerenes and Proteins: The Gd@C60-Lysozyme Model.

Endohedral metallofullerenes (EMFs) have great potential as radioisotope carriers for nuclear medicine and as contrast agents for X-ray and magnetic resonance imaging. EMFs have still important restrictions for their use due to low solubility in physiological environments, low biocompatibility, nonspecific cellular uptake, and a strong dependence of their peculiar properties on physiological parameters, such as pH and salt content. Conjugation of the EMFs with proteins can overcome many of these limitations. Here we investigated the thermodynamics of binding of a model EMF (Gd@C60) with a protein (lysozyme) that is known to act as a host for the empty fullerene. As a rule, even if the shape of an EMF is exactly the same as that of the related fullerene, the interactions with a protein are significantly different. The estimated interaction energy (ΔGbinding) between Gd@C60 and lysozyme is −18.7 kcal mol–1, suggesting the possibility of using proteins as supramolecular carriers for EMFs. π–π stacking, hydrophobic interactions, surfactant-like interactions, and electrostatic interactions govern the formation of the hybrid between Gd@C60 and lysozyme. The comparison of the energy contributions to the binding between C60 or Gd@C60 and lysozyme suggests that, although shape complementarity remains the driving force of the binding, the presence of electron transfer from the gadolinium atom to the carbon cage induces a charge distribution on the fullerene cage that strongly affects its interaction with the protein.

Biocompatibility of Magnetic Resonance Imaging Nanoprobes Improved by Transformable Gadolinium Oxide Nanocoils.

To design functional nanomaterials for biomedical applications, the challenge for scientists is to gain further understanding of their unique toxicological properties. Nonspecific adhesion of proteins and endocytosis are considered to be the major biotoxic sources of imaging nanoprobes. Here, we fabricated ultrathin gadolinium oxide (Gd2O3) nanocoils with a low Young's modulus, which provides transformable properties in solution. The spatial configurational freedom of ultrathin nanocoils induces the steric repulsion to the nonspecific adsorption of proteins that, in turn, suppresses cellular uptake and thus improves their biocompatibility. The larger number of exposed surface gadolinium atoms of the ultrathin nanocoils provided enhanced T1 magnetic resonance (MR) imaging contrast with high signal activation. Such nanocontrast agents were applied to in vivo MR bioimaging to achieve prolonged circulation lifetime. The improved biocompatibility by transformable Gd2O3 nanocoils could open up a new perspective toward the design and construction of various nano-biomedicines in the future.

Crystal structure of a one-dimensional coordination polymer of gadolinium dibromoacetate with 4,4'-bipyridine

A new gadolinium(III) complex with 4,4’-bipyridine (4-bpy) and dibromoacetate ligand of general formula [Gd(4-bpy)(CBr2HCOO)3(H2O)]n, has been synthesized, crystallized and characterized by a single-crystal X-ray diffraction analysis. The gadolinium atom has an unsymmetrical eight-coordinate geometry, being coordinated by six oxygen atoms of dibromoacetate anions, one nitrogen atom of 4-bpy and one water molecule. The complex is a one-dimensional polymer as a result of dibromoacetate ligand bridging with the repeating monomeric units. There are π...π stacking interactions between the 4-bpy rings as well as O–H...O and O–H...N hydrogen bonds. Crystal Data for C16H13Br6GdN2O7 (Mw = 981.99 g/mol): triclinic, space group P-1 (no. 2), a = 9.7368(4) Å, b = 11.5416(4) Å, c = 11.7634(4) Å, α = 104.2750(10)°, β = 94.060(2)°, γ = 92.6900(10)°, V = 1275.08(8) Å3, Z = 2, T = 90 K, μ(CuKα) = 28.190 mm-1, Dcalc = 2.558 g/cm3, 8399 reflections measured (7.782° ≤ 2Θ ≤ 133.18°), 4006 unique (Rint = 0.0409, Rsigma = 0.0639) which were used in all calculations. The final R1 was 0.0527 (I > 2σ(I)) and wR2 was 0.1396 (all data).

Magnetic ground state and optoelectronic properties of GdMg, GdMg2 and GdMg3 investigated by GGA+U calculations

The present work is a study of the magnetic ground state and optoelectronic properties of GdMg, GdMg2 and GdMg3 using FP-(L)APW + lo method as implemented in WIEN2k code. GGA-PBE has been used as exchange-correlation functional for the prediction of structural properties as well as the most stable magnetic phase. The obtained results are in agreement with the previous results; they indicate that at the ground state, GdMg is ferromagnetic whereas GdMg2 and GdMg3 are antiferromagnetic. To ensure a suitable accuracy for the optoelectronic study of these compounds, the effective Coulomb interaction term “U” between 4f-electrons of Gadolinium atom was determined by constrained LDA “cLDA”. The total and partial magnetic moments values confirm the results of the most stable magnetic phase. The electronic study of these compounds indicates that they are all metallic. The optical properties were studied after the determination of the dielectric function of the different compounds taking into account the intra-band transitions which have a significant contribution in metals. Several optical magnitudes have been determined including the possible inter-band and intra-band electronic transitions as well as the evolution of the optical absorption and the refractive index under the effect of excitation by photon energy.

Air-Stable Gadolinium Precursors for the Facile Microwave-Assisted Synthesis of Gd2O3 Nanocontrast Agents for Magnetic Resonance Imaging

Using metal organic precursors in materials synthesis remains a challenge due to their high moisture susceptibility. In this work, we describe a facile methodology for the synthesis of Gd2O3-based contrast agents from two new gadolinium-based complexes. [Gd(PyTFP)4] (PyH) 1 (PyTFP = C8H5NOF3, Py = C5H5N) and [Gd(DMOTFP)3Py] 2 (DMOTFP = C8H7NO2F3) were synthesized via a classical ligand exchange reaction of [Gd{N(SiMe3)2}3] under inert conditions. As a result, X-ray diffraction analysis revealed a distorted square antiprismatic coordination and an augmented triangular prismatic arrangement of ligands around gadolinium atoms in 1 and 2, respectively. It also showed that 1 is an anionic complex of formula [Gd(PyTFP)4](PyH), while a neutral tris-compound, [Gd(DMOTFP)3Py], was obtained as a pyridine adduct in 2. Fast and reproducible microwave-assisted decomposition of 1 and 2 provided homogeneous Gd(OH)3 nanorods at mild temperature without using any surfactant or capping reagent. As-synthesized nanorods were...

Crystal structure of a new binuclear complex of bis(2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane -3,7-dione-O, O′)-diaqua-hexakis(nitrato-O,O′)-digadolinium(III) monohydrate

A centrosymmetric binuclear complex of gadolinium(III) nitrate with bicyclic bisurea (2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar, Mk) [Gd(C8H14N4O2)(H2O)(NO3)3]2·H2O (I) is synthesized and its atomic structure (CIF file CCDC No. 1450653) is determined. The crystals of I are monoclinic: space group P21/c, a = 10.3861(2) A, b = 10.80470(10) A, c = 21.2707(4) A, β = 128.413(3)°, V = 1870.32 A3, ρ(calc.) = 2.05094 g/cm3, Z = 2. The gadolinium atom occupies a general position and is coordinated by two oxygen atoms of two Mk molecules related by a symmetry-center operation, three bidentate nitrate anions, and a water molecule. The coordination polyhedron of the gadolinium atom is a nine-vertex polyhedron represented by a distorted three-cap trigonal prism; the Gd⋯Gd distance in the complex is 6.8697(4) A.

Enhancing Magnetic Functionality with Scandium: Breaking Stereotypes in the Design of Rare Earth Materials

Replacement of strongly magnetic gadolinium with weakly magnetic scandium unexpectedly enhances ferromagnetic interactions in (Gd1–xScx)5Ge4. Based upon this counterintuitive experimental finding we demonstrate the unique role 3d1 electrons of scandium atoms play in mediating magnetic interactions between the gadolinium atoms from the neighboring layers in the Sm5Ge4-type crystal lattice. Scandium substitutions at and below 20% rapidly increase the Curie temperature, TC, of the Gd5Ge4 parent, eliminate both the kinetic arrest and hysteresis, and drastically improve reversibility of the first-order magnetostructural transformation at TC. In agreement with first-principles predictions, higher than 20% Sc leads to the formation of a closely related Pu5Rh4-type structure where the first-order magnetostructural transformation is replaced by a conventional second-order ferromagnetic ordering that remains accompanied by a continuous rearrangement of the crystal lattice. Comparison of two materials with similar s...

Electrochemical Synthesis of Nanomaterials in Molten Salts

For the first time by electrochemical synthesis from NaCl-KCl-NaF-GdF3-KBF4 melt at temperature 1023 K and with utilization of molybdenum cathode the gadolinium hexaboride nanotubes were synthesized. Most likely GdB6 nanotubes formation is ruled by intercalation mechanism. Gadolinium hexaboride lattice is the framework of boron atom octahedrons, in gaps of which the gadolinium atoms are situated. These gaps are spacious enough to host the metal atoms without deformation and even with reserve of vacant space. Electrochemical synthesis of GdB6 occurs at potentials negative enough for alkali metal cations electroreduction. So alkali metal cations intercalate into the emptiness of hexaboride lattice where cations are reduce in situ. The metal atoms have larger radius than its cations so they provoke mechanical strain. At the certain value of the strain GdB6 splits with nanotubes formation. Nanoneedles of TaO with tetragonal crystal lattice were obtained by electrolysis of CsCl melt, containing monooxofluoride complexes of tantalum. It was determined the correlation between the redox potential of molten system, temperature and stability of tantalum monoxide. Multi-layered tantalum boride structures were produced via electrolysis in the NaCl-KCl-NaF-K2TaF7-KBF4 melt. The overall thickness of the layers, synthesized under direct current regime, was 30-50 μm, and they consisted of numerous fine layers (nanolayers). A new generation of highly active and stable catalytic nanostructured coatings for the water-gas shift reaction by high temperature electrochemical synthesis in molten salts has been developed. The steady-state reaction rates for the Mo2C/Mo coatings were higher than those for the bulk Mo2C and commercial Cu/ZnO/Al2O3 catalysts over in the temperature range explored. The catalytic activity is enhanced by at three orders of magnitude comparing to that of the pure Mo2C phase. The methanation reaction was completely suppressed in the whole temperature range studied on the Mo2C/Mo systems. The catalytic activity remained constant during 5000 hours on-stream. The coatings were also stable during the thermal cycling, while the activity of commercial catalysts tends to decrease with time. A novel microstructured reactor/heat-exchanger containing eight sections with a cross-section of 10 mm x 10 mm and a length of 100 mm has been designed and constructed. Each section of the reactor contains flat, perforated Mo plates and Mo wires with a diameter of 250 mm and a length of 100 mm coated with a porous Mo2C layer. Nanoneedles of silicon were obtained in chloride-fluoride melts containing K2SiF6 by potentiostatic electrolysis which accompanied by reaction of disproportionation.

Gallium‐Indium Ordering in the Complex [Ni2Ga3In] Network of GdNi2Ga3In

AbstractPolycrystalline samples of the isotypic quaternary compounds RENi2Ga3In (RE = Y, Gd – Tm) were obtained by arc‐melting of the elements. Crystals of the gadolinium compound were found by slow cooling of an arc‐melted button of the initial composition “GdNiGa3In”. All samples were characterized by powder X‐ray diffraction. The structure of GdNi2Ga2.89In1.11 was refined from single‐crystal X‐ray diffractometer data: new type, Pnma, a = 2426.38(7), b = 418.17(2), c = 927.27(3) pm, wR2 = 0.0430, 1610 F2 values and 88 variables. Two of the six crystallographically independent gallium sites show a small degree of Ga/In mixing. The nickel atoms show tricapped trigonal prismatic coordination by gadolinium, gallium, and indium. Together, the nickel, gallium, and indium atoms build up a complex three‐dimensional [Ni2Ga3In]δ– network, which leaves cages for the gadolinium atoms. The indium atoms form zigzag chains with In–In distances of 337 pm. The crystal chemical similarities of the polyhedral packing in the GdNi2Ga3In and La4Pd10In21 structures are discussed.

Phthalocyanine-based molecular paramagnets. Effect of double-decker structure on magnetothermal properties of gadolinium complexes

Gadolinium is useful in the room temperature magnetic refrigeration due to its large magnetocaloric effect occurring at temperatures close to room. We predict and represent known phthalocyanine complexes as a new class of paramagnets with a large magnetocaloric effect at the temperatures close to room acting due to gadolinium atom located in a coordination site of a conjugated phthalocyanine macrocycle/macrocycles. Magnetothermal properties (a magnetocaloric effect, specific heat capacity, heat released due to MCE, enthalpy/entropy change) of paramagnetic (AcO)GdPc and GdPc2, Pc – phthalocyanine dianion, as the 3% water suspensions at 278–338 K in the magnetic fields of 0–1.0 T were studied for the first time in the family of these paramagnets. The study of magnetothermal properties and specific heat capacity were performed in two independent experiments by microcalorimetry and differential scanning calorimetry, respectively. Large positive MCE in (AcO)GdPc reaches a value of 0.47 K at 278 K when the magnetic field is changed from 0 to 1 T. MCE in GdPc2 is lower by almost an order of magnitude compared with (AcO)GdPc, which indicates that the intramolecular oxidation-activated spin coupling does not prevail over the intermolecular coupling of two radical spins.

5 7 Fe Emission Mössbauer Study on Gd 3 Ga 5 O 1 2 implanted with dilute 5 7 Mn

57Fe emission Mossbauer spectroscopy has been applied to study the lattice location and properties of Fe in gadolinium gallium garnet Gd3Ga5 O 12 (GGG) single crystals in the temperature interval 300 – 563 K within the extremely dilute (<10−4 at.%) regime following the implantation of57Mn (T 1 / 2= 1.5 min.) at ISOLDE/CERN. These results are compared with earlier Mossbauer spectroscopy study of Fe-doped gadolinium gallium garnet Gd3Ga5 O 12(GGG), with implantation fluences between 8×1015 and 6×1016 atoms cm−2. Three Fe components are observed in the emission Mossbauer spectra: (i) high spin Fe2+ located at damage sites due to the implantation process, (ii) high spin Fe3+ at substitutional tetrahedral Ga sites, and (iii) interstitial Fe, probably due to the recoil imparted on the daughter57∗Fe nucleus in the β − decay of57Mn. In contrast to high fluence57Fe implantation studies the Fe3+ ions are found to prefer the tetrahedral Ga site over the octahedral Ga site. No annealing stages are evident in the temperature range investigated. Despite the very low concentration, high-spin Fe3+ shows fast spin relaxation, presumably due to an indirect interaction between nearby gadolinium atoms.